Superchargers are often installed in vehicles and other machines with internal combustion engines to increase the engines' horsepower output. Superchargers increase the volume of air delivered to the cylinders of the engines during their intake cycles, thereby increasing the density or pressure of the air during the engines' compression and ignition strokes. Superchargers include air blowers or compressors that are driven directly or indirectly by their associated engines. Thus, as the speed of an engine increases, the speed of its supercharger proportionally increases. Due to the wide variation in engine speeds, typically from around 700 R.P.M. at idle to 8,000 R.P.M and higher at “red-line” acceleration, a supercharger also operates at wide variety of speeds.
High performance enthusiasts often wish to control the precise boost pressure of superchargers at different engine speeds to obtain desired engine power enhancements across all engine speeds. It is known to drive superchargers with continuously variable transmissions (CVTs) in order to provide a substantially constant drive speed to the superchargers. However, attempts to control CVTs to provide selectable supercharger drive speeds at different engine speeds have been mostly unsuccessful for a variety of reasons.